The invention relates to an apparatus comprising a transmitter unit with which the position of a medical instrument can be determined with the aid of a CAS system. The apparatus comprises the transmitter unit at a fixed location and the apparatus can be attached to the medical instrument.
Such an apparatus is disclosed in the article by Cinquin, P. et al.: xe2x80x9cComputer Assisted Medical Interventionxe2x80x9d, IEEE Engineering in Medicine and Biology, May/June 1995, pages 256 to 263.
So-called CAS systems (computer assisted surgery) are increasingly used in various operations, for example in neurosurgery, spinal surgery and surgery relating to the throat, nose and ears. Such systems are also indicated with the abbreviation CAMI=computer assisted medical intervention. These CAS systems consist at least of a position sensor unit which detects the position and/or the direction of an instrument, for example an endoscope, and transmits this information to an image processing unit in which data in the form of CT, MR and/or ultrasound images of the body region to the be treated are present in three dimensionals. After reference markings are correlated with three dimensional image data corresponding to the original position data, a correct position determination of instruments is possible in the image data set. The operator thus has the possibility to orient himself during an operation on the basis of image data reproduced on a monitor. A prerequisite for precise localization, apart from the accuracy of the position detection, is especially the geometric invariance of the body structure from the time the image data is taken until the time of the operation. Thus this method is especially suitable for operations in which rigid body structures are involved and the shifting capability of soft tissue is small, i.e. for operations on the skull, on the spine or the sinuses.
The position detection in the above-mentioned apparatus is effected by means of several radiating diode or position elements, whose signals can be detected from remote cameras and supplied to a computer.
The position of the diodes and thus the position of the instrument connected directly thereto is determined with the triangulation method in the computer. The transmitter unit must be connected at a fixed position with the instrument, for example an endoscope whose position is to be determined. This connection must remain invariable during the operation. In the abovementioned apparatus, a total of six diodes are arranged on an approximately T-shaped or sword-shaped bulky and voluminous component, which is attached in the region of a shaft of the respective instrument, namely either on the shaft of an endoscope or on the shaft of a borer. The apparatus can be positioned along the shaft and its position fixed by screws employing a sleeve covering the shaft.
A disadvantage of the known apparatus is that the mounting procedure and the change of the transmitter unit to another instrument, for example to another endoscope, are very time consuming and complicated. Such a change is only possible with considerable effort, especially under clinical conditions during an operation and under the requirements on sterility.
Several instruments are often employed in certain operations and in the course of an operation it is necessary to re-use an instrument employed at the beginning, which in the meantime has been set aside. For example, if the instrument is an endoscope with a so-called straight view, then this endoscope can be used at the beginning of the operation to approach an operation site by inserting along the endoscope axis, for example through the nose to a site in the sinus cavity. Should an operation then be carried out on a tumor located to the side of the operation site, the endoscope with the straight view is replaced with an endoscope having a side view.
Should the operation area be inspected again for remaining objects at the end of the operation, the initial endoscope with the straight view is required again. In addition, the change from or to a passive instrument is also frequently necessary, for example when a trocar with an obturator is to be inserted, i.e. without viewing.
Each instrument must be provided with numerous, at least three, transmitters in order to be able to determine the position of the respective instrument. This is complicated and expensive. Consequently, numerous coupling and decoupling procedures of the components of the medical instruments must be made during an operation. The components coupled to an endoscope are mainly cameras, which are connected to a processor unit and a monitor with cables. The problem of contamination of the sterile instruments arises due to the non-sterile components, such as cameras or the like.
The object of the present invention is therefore to provide an improved apparatus of the above-mentioned type, where the position detection of the respective instrument is carried out precisely and with little effort and where the coupling and decoupling between parts of the medical instruments and the CAS system are carried out in simple, rapid and reliable manner under sterile conditions.
According to the present invention, the apparatus is configured as an adapter comprising a reception coupling on a first side, with which it can simply be coupled to a predetermined connecting location on the medical instrument in releasable, but mechanically fixed manner.
It is no longer necessary to provide a transmitter unit on each instrument, but only necessary to couple the adapter to the instrument to be detected, which can be accomplished by a simple procedure. The adapter need only be placed upon the corresponding connecting location present on the instrument and coupled thereto, which can be performed in a clip-on manner. The adapter can be coupled to the most different types of instrument, where these only require the corresponding connecting locations for the adapter. Various instruments can now be coupled to an adapter during an operation or decoupled therefrom, which is very simple, does not require great concentration and is also very fast. Should the position of the distal end be detected, then the only necessary information when changing the instrument is how far the tip is removed from the adapter, which can be determined by the CAS system itself through corresponding input data and memory data in the processor unit or through corresponding instrument specifications.
The provision of this adapter now opens the possibility of separating at a defined location sterile portions of the medical instrument system, for example an endoscope, from non-sterile portions, for example a camera with connecting cables to monitors in the operating room. One only needs to adjust the adapter with its transmitter unit to the detection system of the CAS system, and then any properly configured instruments can be coupled to the adapter.
This considerably increases the flexibility in such operations and at the same time simplifies the operation of the CAS system with the corresponding array of instruments.
In a preferred embodiment of the invention, the adapter comprises at least one further reception coupling, with which it can be coupled to a further medical instrument. The feature has the advantage that the adapter including the transmitter unit can be employed at a favorable, intermediate position within the instrument system. Favorable means that the position is favorable for detection of the transmitter location of the transmitter unit and/or a favorable ergonomic arrangement without disturbing the operator.
In a further embodiment of the invention, the adapter is configured such that on a first side, it can be coupled to a proximal end of an instrument whose position is to be detected through the transmitter unit. The feature has the advantage that the adapter is coupled at an easily accessible location, where the instrument is not disturbed in its handling capabilities. To exchange the instrument, the connection is simply released and another instrument is coupled to the adapter at its proximal end.
In a further embodiment of the invention, the adapter at a second side is formed as the proximal end of the instrument, which can be coupled to the first side of the adapter. This has the considerable advantage that no constructive alterations of the components are necessary, for example a camera, which normally is directly connected to the instrument, for example an endoscope.
It is also possible to still use existing or standardized components and the present adapter need only be connected therebetween. This not only simplifies the CAS system, but is also very inexpensive.
In a further embodiment of the invention, the adapter comprises a reception coupling on its first side for coupling to an ocular cup. In this form, the adapter is suited for simple connection to the most often used instrument in endoscopic operations, namely an endoscope. The adapter can be simply coupled to existing, common endoscope systems because endoscopes of different types from one manufacturer or from several manufacturers usually have standardized ocular cups. An ocular cup offers a relatively large, approximately ring-shaped coupling surface, so that the adapter can be simply and securely attached and a very exact position detection is possible when coupled to various models of endoscopes.
In a further embodiment of the invention, the adapter comprises a reception coupling on its second side in the form of an endoscope ocular cup. The feature has the considerable advantage that the adapter on the second side is formed as the mentioned standardized ocular cup, and therefore can be simply coupled to the corresponding standardized coupling location on cameras. Here again, the ocular cup geometry allows a relatively large and geometrically favorable attachment surface, namely in circular form. Thus a particularly simple, rapid and exactly fitting can be made on this side with the further components, so that the adapter on the whole and thus the transmitter unit is integrated in exact position in the endoscopic system.
Embodiments are also possible in which the actual ocular cup is much smaller than the standard ocular cup as is common in pure video endoscopy.
In a further embodiment of the invention, the adapter is configured such that image transmission is possible between the coupling locations where the adapter connects the two components of the endoscopic system. This feature has the considerable advantage that the intermediate adapter makes image transmission possible, if the instrument is an endoscope, and the image is not negatively influenced or disturbed. The adapter thus also fulfills a further function, namely it enhances undisturbed and exact image transmission.
Further optical elements, particularly imaging elements or filters can be arranged in the adapter in advantageous manner.
In a further embodiment of the invention, an optical window is arranged between the coupling locations of the adapter, so that one coupling location can be hermetically separated from the other coupling location.
This feature has the considerable advantage that the adapter with the optical window serves as a separator, for example between the sterile instrument and the non-sterile camera, that it is ensured at the same time that an image can be transmitted when the instrument is an endoscope, and that it is ensured that despite several exchanges of the instrument during an operation, the two instruments coupled by the adapter are hermetically separate from one another, so that no contamination can be transmitted from one to the other. This contributes not only to simple handling but also to hygienically safe operation of the endoscopic system.
In a further embodiment of the invention, the reception coupling for connection of the instrument to be detected is configured to be self-centering. The feature has the advantage that when exchanging the instrument, the operator need not pay close attention to the exchange and connection steps, but only need to place the instrument on the corresponding coupling location of the adapter and for example apply pressure or push the instrument. The coupling itself takes care of the centering. This is particularly favorable for image transmission because the optical axis of the instrument then exactly corresponds to the optical axis of the adapter.
In a further embodiment of the invention, the position errors caused by the dimensional tolerances of the reception coupling following the coupling procedure are small. The feature has the advantage that the position detection error caused by the tolerances is extremely small. In particular, exactly fitted connections without large radial or axial play can be achieved with the above-mentioned geometries, i.e. the round ocular cuplike coupling locations, while it is still ensured that easily accessible and simple coupling procedures can be carried out.
In a further embodiment of the invention, the position errors of the reception couplings are reproducible. This feature has the advantage that corresponding computer defined corrections can be made on the basis of these reproducible deviations, where the deviations are accounted for in the total measurement accuracy of the CAS system.
In a further embodiment of the invention, the reception coupling for connecting an instrument is configured such that the two components can only be coupled to one another in a certain relative position. In some instruments, for example endoscopes with a side view, the distal end piece is not exactly perpendicular to the center axis of the endoscope shaft, but inclined thereto. This means that images are taken from sites which are closer or further away from the proximal end of the endoscope. It is then desirable that the endoscope be coupled in a single particular angular position relative to the adapter or to the camera attached thereto, which is easy to accomplish with corresponding orientation elements on the adapter.
In a further embodiment of the invention, the transmitter unit is attached to the adapter such that its transmitter is arranged in a direction transverse to the longitudinal axis of the instrument. The feature has the advantage that all transmitters have about the same distance to the tip of the instrument, so that inherent system errors influencing the length of the distance are about equal and thus can also be computationally suppressed or eliminated. The localization error increases with increasing distance between the position to be localized, i.e. the tip of the instrument, and the transmitters. Thus the arrangement of the transmitter unit transversely on the adapter, which is attached at the proximal end of the instrument, provides a good solution because this distance is not so large and at the same time, the freedom in handling the instrument is not impaired by the adapter with its transmitter unit. For example, the entire length of the endoscope shaft remains unhindered by the adapter. This configuration is ergonomic and saves space.
In a further embodiment of the invention, the transmitter unit is approximately bar-shaped and extends in transverse direction to the optical axis of the adapter. The feature has the advantage that the transmitter unit is formed in compact construction and the handling of the adapter is simplified. The configuration is particularly ergonomic and especially favorable with respect to the construction length.
In a further embodiment of the invention, the transmitter unit is arranged such that its transmitters lie along the longitudinal axis of the instrument. The feature has the advantage that the basic lengths for determining the tip of the instrument are relatively long and therefore the measurement error is small. The accuracy of determining the angular position about the instrument axis is then smaller, but the angular position as such is often less accurate to detect. A distribution along the instrument axis leads to a slender construction and the view along the longitudinal axis is less hindered.
In a further embodiment of the invention, the transmitters of the transmitter unit are distributed on a surface. The feature has the advantage that the highest possible accuracy of position detection is possible.
In a further embodiment of the invention, the transmitter unit comprises transmitters known per se which send out ultrasound, IR or other electromagnetic radiation. This feature has the advantage that a contactless detection of position can take place via radiation or fields emitted by the transmitters to cameras or other suitable sensors in the operation room.
In a further embodiment of the invention, the transmitter unit comprises transmitters including passively reflecting elements or transmitters which can be activated by radiation. The feature has the advantage that the passively reflecting elements do not require an energy supply which strongly influences the constructive design of the adapter. Actively radiating transmitters require either an energy source in the form of batteries or a cable connection to an external energy source, which is disturbing. Radiation-activated transmitters, for example configured as transponders also do not require their own energy supply.
It will be understood that the above-mentioned features and those to be discussed below are not only applicable in the given combinations but may be employed in other combinations or taken alone without departing from the scope of the present invention.